/*
 * Licensed to the Apache Software Foundation (ASF) under one
 * or more contributor license agreements.  See the NOTICE file
 * distributed with this work for additional information
 * regarding copyright ownership.  The ASF licenses this file
 * to you under the Apache License, Version 2.0 (the
 * "License"); you may not use this file except in compliance
 * with the License.  You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package org.apache.flink.runtime.util;

import org.apache.flink.api.java.tuple.Tuple2;
import org.apache.flink.configuration.ConfigConstants;
import org.apache.flink.util.FlinkRuntimeException;
import org.apache.flink.util.Preconditions;

import org.apache.hadoop.conf.Configuration;
import org.apache.hadoop.hdfs.HdfsConfiguration;
import org.apache.hadoop.io.Text;
import org.apache.hadoop.security.UserGroupInformation;
import org.apache.hadoop.security.token.Token;
import org.apache.hadoop.security.token.TokenIdentifier;
import org.apache.hadoop.util.VersionInfo;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

import java.io.File;
import java.util.Collection;

/**
 * Utility class for working with Hadoop-related classes. This should only be used if Hadoop
 * is on the classpath.
 */
public class HadoopUtils {

	private static final Logger LOG = LoggerFactory.getLogger(HadoopUtils.class);

	static final Text HDFS_DELEGATION_TOKEN_KIND = new Text("HDFS_DELEGATION_TOKEN");

	@SuppressWarnings("deprecation")
	public static Configuration getHadoopConfiguration(org.apache.flink.configuration.Configuration flinkConfiguration) {

		// Instantiate an HdfsConfiguration to load the hdfs-site.xml and hdfs-default.xml
		// from the classpath

		Configuration result = new HdfsConfiguration();
		boolean foundHadoopConfiguration = false;

		// We need to load both core-site.xml and hdfs-site.xml to determine the default fs path and
		// the hdfs configuration.
		// The properties of a newly added resource will override the ones in previous resources, so a configuration
		// file with higher priority should be added later.

		// Approach 1: HADOOP_HOME environment variables
		String[] possibleHadoopConfPaths = new String[2];

		final String hadoopHome = System.getenv("HADOOP_HOME");
		if (hadoopHome != null) {
			LOG.debug("Searching Hadoop configuration files in HADOOP_HOME: {}", hadoopHome);
			possibleHadoopConfPaths[0] = hadoopHome + "/conf";
			possibleHadoopConfPaths[1] = hadoopHome + "/etc/hadoop"; // hadoop 2.2
		}

		for (String possibleHadoopConfPath : possibleHadoopConfPaths) {
			if (possibleHadoopConfPath != null) {
				foundHadoopConfiguration = addHadoopConfIfFound(result, possibleHadoopConfPath);
			}
		}

		// Approach 2: Flink configuration (deprecated)
		final String hdfsDefaultPath =
			flinkConfiguration.getString(ConfigConstants.HDFS_DEFAULT_CONFIG, null);
		if (hdfsDefaultPath != null) {
			result.addResource(new org.apache.hadoop.fs.Path(hdfsDefaultPath));
			LOG.debug("Using hdfs-default configuration-file path from Flink config: {}", hdfsDefaultPath);
			foundHadoopConfiguration = true;
		}

		final String hdfsSitePath = flinkConfiguration.getString(ConfigConstants.HDFS_SITE_CONFIG, null);
		if (hdfsSitePath != null) {
			result.addResource(new org.apache.hadoop.fs.Path(hdfsSitePath));
			LOG.debug("Using hdfs-site configuration-file path from Flink config: {}", hdfsSitePath);
			foundHadoopConfiguration = true;
		}

		final String hadoopConfigPath = flinkConfiguration.getString(ConfigConstants.PATH_HADOOP_CONFIG, null);
		if (hadoopConfigPath != null) {
			LOG.debug("Searching Hadoop configuration files in Flink config: {}", hadoopConfigPath);
			foundHadoopConfiguration = addHadoopConfIfFound(result, hadoopConfigPath) || foundHadoopConfiguration;
		}

		// Approach 3: HADOOP_CONF_DIR environment variable
		String hadoopConfDir = System.getenv("HADOOP_CONF_DIR");
		if (hadoopConfDir != null) {
			LOG.debug("Searching Hadoop configuration files in HADOOP_CONF_DIR: {}", hadoopConfDir);
			foundHadoopConfiguration = addHadoopConfIfFound(result, hadoopConfDir) || foundHadoopConfiguration;
		}

		if (!foundHadoopConfiguration) {
			LOG.warn("Could not find Hadoop configuration via any of the supported methods " +
				"(Flink configuration, environment variables).");
		}

		return result;
	}

	public static boolean isKerberosSecurityEnabled(UserGroupInformation ugi) {
		return UserGroupInformation.isSecurityEnabled() && ugi.getAuthenticationMethod() == UserGroupInformation.AuthenticationMethod.KERBEROS;
	}

	public static boolean areKerberosCredentialsValid(UserGroupInformation ugi, boolean useTicketCache) {
		Preconditions.checkState(isKerberosSecurityEnabled(ugi));

		// note: UGI::hasKerberosCredentials inaccurately reports false
		// for logins based on a keytab (fixed in Hadoop 2.6.1, see HADOOP-10786),
		// so we check only in ticket cache scenario.
		if (useTicketCache && !ugi.hasKerberosCredentials()) {
			if (hasHDFSDelegationToken(ugi)) {
				LOG.warn("Hadoop security is enabled but current login user does not have Kerberos credentials, " +
					"use delegation token instead. Flink application will terminate after token expires.");
				return true;
			} else {
				LOG.error("Hadoop security is enabled, but current login user has neither Kerberos credentials " +
					"nor delegation tokens!");
				return false;
			}
		}

		return true;
	}

	/**
	 * Indicates whether the user has an HDFS delegation token.
	 */
	public static boolean hasHDFSDelegationToken(UserGroupInformation ugi) {
		Collection<Token<? extends TokenIdentifier>> usrTok = ugi.getTokens();
		for (Token<? extends TokenIdentifier> token : usrTok) {
			if (token.getKind().equals(HDFS_DELEGATION_TOKEN_KIND)) {
				return true;
			}
		}
		return false;
	}

	/**
	 * Checks if the Hadoop dependency is at least the given version.
	 */
	public static boolean isMinHadoopVersion(int major, int minor) throws FlinkRuntimeException {
		final Tuple2<Integer, Integer> hadoopVersion = getMajorMinorBundledHadoopVersion();
		int maj = hadoopVersion.f0;
		int min = hadoopVersion.f1;

		return maj > major || (maj == major && min >= minor);
	}

	/**
	 * Checks if the Hadoop dependency is at most the given version.
	 */
	public static boolean isMaxHadoopVersion(int major, int minor) throws FlinkRuntimeException {
		final Tuple2<Integer, Integer> hadoopVersion = getMajorMinorBundledHadoopVersion();
		int maj = hadoopVersion.f0;
		int min = hadoopVersion.f1;

		return maj < major || (maj == major && min < minor);
	}

	private static Tuple2<Integer, Integer> getMajorMinorBundledHadoopVersion() {
		String versionString = VersionInfo.getVersion();
		String[] versionParts = versionString.split("\\.");

		if (versionParts.length < 2) {
			throw new FlinkRuntimeException(
					"Cannot determine version of Hadoop, unexpected version string: " + versionString);
		}

		int maj = Integer.parseInt(versionParts[0]);
		int min = Integer.parseInt(versionParts[1]);
		return Tuple2.of(maj, min);
	}

	/**
	 * Search Hadoop configuration files in the given path, and add them to the configuration if found.
	 */
	private static boolean addHadoopConfIfFound(Configuration configuration, String possibleHadoopConfPath) {
		boolean foundHadoopConfiguration = false;
		if (new File(possibleHadoopConfPath).exists()) {
			if (new File(possibleHadoopConfPath + "/core-site.xml").exists()) {
				configuration.addResource(new org.apache.hadoop.fs.Path(possibleHadoopConfPath + "/core-site.xml"));
				LOG.debug("Adding " + possibleHadoopConfPath + "/core-site.xml to hadoop configuration");
				foundHadoopConfiguration = true;
			}
			if (new File(possibleHadoopConfPath + "/hdfs-site.xml").exists()) {
				configuration.addResource(new org.apache.hadoop.fs.Path(possibleHadoopConfPath + "/hdfs-site.xml"));
				LOG.debug("Adding " + possibleHadoopConfPath + "/hdfs-site.xml to hadoop configuration");
				foundHadoopConfiguration = true;
			}
		}
		return foundHadoopConfiguration;
	}
}
